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Zn II Complex with a Phenanthroline‐Containing Macrocycle as Receptor for Amino Acids and Dipeptides − Hydrolysis of an Activated Peptide Bond
Author(s) -
Bazzicalupi Carla,
Bencini Andrea,
Berni Emanuela,
Bianchi Antonio,
Fornasari Patrizia,
Giorgi Claudia,
Valtancoli Barbara
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200200648
Subject(s) - chemistry , moiety , peptide bond , stereochemistry , dipeptide , peptide , ligand (biochemistry) , carboxylate , amino acid , amide , hydrolysis , phenanthroline , medicinal chemistry , crystallography , organic chemistry , receptor , biochemistry
The interaction between several L ‐amino acids and dipeptides and the Zn II complex with ligand L, a macrocycle containing a triamine chain linking the 2,9 positions of a phenanthroline moiety, has been studied by means of potentiometric and 1 H NMR spectroscopic measurements in aqueous solutions. In the [ZnL] 2+ complex, the metal ion displays an unsaturated coordination environment and the metal can act as a binding site for these substrates. Amino acids and dipeptides in their neutral (zwitterionic) form bind to Zn II through the carboxylate function and, when in their anionic form, through the amine group. In this case the carbonyl of the amide function is probably also involved in metal coordination. Amino acids containing aromatic pendants form the most stable complexes, due to hydrophobic and/or π‐stacking interactions between the aromatic subunits of the substrates and the phenanthroline moiety of the metal receptor. The hydrolytic properties of the Zn II complex with L, involving the cleavage of the peptide bond, have been tested by using L ‐leucine‐ p ‐nitroanilide (LNA), which contains an activated peptide bond. This substrate forms stable [ZnL(LNA)] 2+ and [ZnL(OH)(LNA)] + complexes. The formation of the [ZnL(OH)(LNA)] + complex is followed by LNA hydrolysis, through a nucleophilic attack of the Zn−OH function on the peptide bond. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)